Quick drying ink



Patented Oct. 31, 1944 QUICK DRYING INK Herbert J. Wolfe, Maspeth', and Paul W. Greubel,

Long Island City, N. Y., assignors to American Can Company, New'York, N. Y., a corporation of New Jersey No Drawing. Application July 2, 1941, Serial No. 400,860

1 Claim. 10626) The present invention relates to a new and useful ultra-fast drying printing ink which when heated dries by evaporation resulting in gelation and has particular reference to a rapid drying nitrocellulose base ink.

The great majority of typographic printing presses are designed to be used with convntional pigment-and-oil inks which dry by absorbing oxygen from the surrounding air. This type of ink, even when made from relatively fast drying'synthetic oils and resins, requires a considerable time to dry. This time may vary from a few minutes to many hours. Since on most printing presses, the freshly printed material travels for only a few seconds and/or a few feet before it is either rewound or stacked, the chances for offsetting of the ink from the printed to the unprinted sides of the material are considerable. offsetting is very undesirable since it ruins the appearance of the printed work and in some cases causes the printed material to stick together.

There are many methods used in the printing art for reducing offset, such as adding various waxes and compounds to the inks, spraying the freshly printed surfaces with molten wax or with solutions of gums, starches, etc., and by the use of various static-removing devices which prevent the freshly printed sheets, or web, from clinging together due to electrostatic charges picked up by the printed material during its passage through the presses.

However, these methods of preventing offset are rendered ineffective if the freshly printed portions of the material are rubbed against the unprinted, or reverse, side of the material as occurs when the freshly printed sheets are removed from the stacking mechanism of the presses, or when the freshly printed rolls are wound too tightly. Obviously, the only positive way to eliminate offset is to'dry the inks thoroughly before they reach the stacking mechanisin or rewind rolls of the presses.

There are several types of very fast drying inks used in the printing art at the present time, such as anilin inks and intaglio inks, but these are all highly fluid and do not lend themselves to use on presses equipped with key-set fountains, distributing rollers and usual metal type. These inks would dry up on the distributing mechanism of these presses before the ink could reach the material being printed. There are also the so-called heat-set or flash-dry types of inks which are suitable for use on ordinary typographic presses but which require the application of considerable heat for appreciable periods of time to cause them to dry. These inks pass through a tacky, or sticky stage in drying and if the inks are not thoroughly dry before stacking or rewinding serious offsetting and sticking occur.

The present invention is directed to the provision of a unique type of ink which depends upon the phenomenon of drying by gelation accelerated as desired by heat. The heat serves merely to volatilize a portion of the solvent sufficient to cause gelation of the remaining ingredients. It is not necessary to volatilize more than a very small percentage of the total solvent in the ink to cause gelation to ensue. The printed surface never passes through a tacky or sticky stage during drying. The drying of the ink is a matter of a fraction of a second rather than minutes or hours. At the same time, the ink is sufficiently stable or non-drying on the press to adapt it for use on ordinary commercial typographic presses.

, The greatest advantage of using an ink embodying the present invention is the prevention of offsetting of the printed surface which permits stacking or rewinding immediately after printing. This is made possible by a thorough drying of the ink almost instantaneously after printing by the application of a moderate amount of heat. In other words, the use of such an ink permits complete time control of the drying and stacking or rewinding operations. This is a great advantage in high speed printing.

An object of the present invention is the provision of an ultra-fast drying printing ink based on nitrocellulose dissolved in a moderately lowboiling solvent, that is, one that boils below 202 degrees centigrade, at 760 millimeters pressure, which at the same time is sufilciently stable or non-drying on the press as to adapt it to the printin operation on commercial typographic printing presses.

Another object of this invention is the provision of an ink of this character which dries so rapidly under the influence of a moderate amount of heat as to eliminate offsetting.

Still a third object is the provision of such an ink which dries so rapidly as to permit of stacking or rewinding almost immediately after printing.

Numerous other objects and advantages of the invention will be apparent as.it is better understood from the following description which is of a preferred embodiment thereof.

The principal ingredients of the ultra-fast drying ink of the present invention are nitrocellulose and certain moderately low-boiling solvents such as the mono-ethyl ether of ethylene glycol or the mono-ethyl ether of diethylene glycol. The nitrocellulose is preferably of the second ester-soluble type, known in the trade as the "RS" type, although other grades and viscosities may be employed also. lulose is dissolved in the solvents, in the proportions hereafter set forth and such a solution forms a vehicle in which varying percentages of pigments may be ground to form printing inks. A small amount of wax, preferably paraffin wax, is generally added to the inks to retard evaporation on the printing press and to impart additional slip, or lubrication; to the printing.

This wax may be added to the inks in the form of a compound made by dissolving 20 parts by weight of paraffin wax into 80 parts by weight of castor oil.

We are aware that nitrocellulose has been used in printing inks. However, in every case, it is believed, high-boiling solvents, for instance the mono-butyl ether of ethylene glycol or the monobutyl ether of di-ethylene glycol have been used in an attempt to achieve stability, 1. e., non-drying of the ink on the press. These solvents all boil between 202 and 300 degrees centigrade. Naturally the presence of such high-boiling solvents retards the drying of the inks on the printed surfaces as well as on the press prior to printing and are therefore not as desirable as the lower-boiling solvents employed in the present invention.

An example of a, workable formula embodying the present invention follows:

Pounds Mono-ethyl ether of ethylene glycol 12 Mono-ethyl ether of di-ethylene glycol 36 %-second RS nitrocellulose (wet with 30% ethanolle 8.

Pigment, for instance, lithol red toner 20 Paraflln wax compound, as mentioned above- '3 In preparing the ink from the above identified materials, the -second RS nitrocellulose, which has been wetted with 30 percent of ethanol by the manufacturer to render it safer to handle, is dissolved in the mixture of mono-ethyl ether of ethylene glycol and mono-ethyl ether of iii-eth- The nitroceldinary printing inks.

formula one part of the mono-ethyl ether of ethylene glycol is shown for three parts of the monoethyl ether of diethylene glycol. Practically the same ink may be obtained when the amounts of these two solvents are equal, or when the ink is prepared from either one of the solvents alone. The pigment portion ofthe ink, too, may be varied within wide limits without altering the substance of the invention. Practically any pigment combination may be employed so long as there is sumcient vehicle present to form a workable ink.

Since the inks embodied in the present invention dry by gelation in a fraction of a second upon the application of heat, all danger of offsetting is avoided and the printed matter may be stacked or rewound on rolls in a remarkably short time after printing. The heat desired will vary in intensity with the time of drying. Where high speed printing is being run, greater heat is needed. As an example, when the printed surface is to be dried in the fraction of a second, the intense heat from a high pressure gas burner may be used.

The ink of the present invention has other vaiuable characteristics which set it apart from or- While it is stable and free flowing in the ordinary printing press, it does not cause trouble even when left to dry on the rollers when the press is stopped. In such a case it is necessary merely to start the press again and fresh ink descending from the ink fountain re-dissolves the ink and makes it workparaflin wax compound is then added and the I mixing is continued until all ingredients are wetted out. The mass is then passed over an ink mill until a smooth, homogeneous ink results. This completes the steps in the preparation of the ink.

The above quantities are given by way of example only and it has been found that some latitude may be had without adversely affecting the quality of the ink. For example, in the above able. The drying of the ink on the rollers during extensive shut-downs may be prevented altogether by spraying the rollers with a small amount of the mono-ethyl ether of ethylene glycol immediately after stopping the press.

Furthermore, the improved ink of the present invention is economical to use since there is no loss due to skinning of the ink surfaces. By reason of this quality of non-skinning of the ink surfaces, washing of the ink from the rollers or other parts of the press is easier than with conventional printing inks. Another advantage of these new inks is that they are odor-free, particularly when dried.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description, and it will be apparent that various changes may be made in the matter of the ingredients, their identity and their proportions without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof.

We claim:'

A printing ink adapted for rapid drying by evaporation resulting in gelation without passing through the stage of tackiness, consisting of approximately 20 parts by weight of a pigment dispersed in a vehicle composed of approximately 8 parts by weight of nitrocellulose dissolved in approximately 12 parts by weight of mono-ethyl ether of ethylene glycol and 36 parts by weight of mono-ethyl ether of di-ethylene glycol with the addition of approximately 3 parts by weight of a paraffin wax compound.

HERBERT J. WOLFE. PAUL W. GREUBEL. 

